The present invention relates to a film forming method for coating a photo-resist film or an anti-reflective coating on a layer (such as a semiconductor layer, an insulating layer, an electrode layer, or the like) formed on a surface of a substrate or a substrate for a liquid crystal display (LCD).
A photo-lithography technique is used in a process for manufacturing a LCD, like in a process for manufacturing a semiconductor device. In the photo-lithography technique for a LCD, a resist film is formed on a glass substrate and is subjected to pattern exposure and further to development. The semiconductor layer, the insulating layer, the electrode layer, or the like is selectively etched to form thin films and electrode patterns made of ITO.
In general, a so-called spin-coating method is used in case of applying a resist solution onto a LCD substrate. As shown in FIG. 1A, a substrate G is suctioned and maintained by a spin-chuck 701 in the spin-coating method, and both of a solvent and a resist solution 9 are dropped onto a rotation center portion of the substrate G. Subsequently, as shown in FIG. 1B, an upper opening is closed with a lid 713, and a rotation cup 711 and a spin chuck 701 are synchronously rotated. In this manner, as shown in FIG. 2A, the resist solution 9 is diffused from the rotation center portion to the peripheral portion and is thereby coated over the entire upper surface of the substrate G.
When the resist solution 9 must be diffused so as to draw a circle covering the four corner portions of the substrate as shown in FIG. 2B if the resist solution 9 should be applied to the entire substrate G, since the substrate G has a rectangular shape. In the case of diffusing the resist solution to the hatched regions R1 to R4 in the figure, the resist solution 9 is wasted.
However, if the supply amount of the resist solution 9 is decreased too much, the resist solution 9 does not sufficiently reach the corner portions of the substrate G. Therefore, it is conventionally necessary to supply an excessive amount of resist solution 9, and about 90% of the supply amount of the resist solution 9 is disposed of.
In case where the resist is coated in spin-coating method, however, the resist film is thickened to rise at the peripheral edge portion of the substrate due to influences from the surface tension after rotation stops to stop the centrifugal force or as the time is elapsed although the film thickness is uniform immediately after the film is coated. Also, in this method, an excessive portion of resist is shaken off by rotation of the substrate, and the portion of resist thus shaken off is diffused onto the back surface of the substrate so that the resist may stick to unnecessary portions.
Thus, a non-uniform thick film formed at the peripheral portion of the substrate and a resist sticking to the back surface thereof cause generation of particles in a later step of conveying the substrate, and may further soil devices for conveying the substrate.
Therefore, after a resist is coated on the surface of the substrate, processing of removing unnecessary resists sticking to the peripheral edge portion and the back surface of the substrate. This processing is performed after coating the resist, in a manner in which the substrate is conveyed to a resist remover unit adjacent to the resist coating unit, a resist remover nozzle comprising a solvent supply portion and a solvent suction portion is moved along the peripheral edge of the substrate, a solvent for the resist is supplied, and simultaneously, the resist dissolved by supply of the solvent is suctioned and removed.
However, in case of removing a resist using the apparatus as described above, the resist coating unit requires an additional equipment so that the size of the equipment must be inevitably enlarged. In addition, the nozzle must be moved with the substrate inserted in a narrow gap between the solvent supply portion and the solvent suction portion of the resist remover nozzle. Therefore, the accuracy of the positions of the substrate and the nozzle relative to each other must be high. Demands for such position accuracy become higher and higher as the size of the substrate has come to be enlarged in recent days.
The present invention has an object of providing a film forming method capable of reducing the consumption of a process liquid where a film having a uniform film thickness is formed on a substrate.
A coating film forming method comprising the steps of: (a) rotatably holding a substrate by a spin chuck; (b) supplying a solvent for a coating film to a first portion deviated from a rotation center portion of the substrate; (c) supplying a process liquid to a second portion which is at the rotation center of the substrate; and (d) diffusing the process liquid from the second portion to a periphery thereof by rotating the substrate.
Another coating film forming method comprising the steps of: (g) rotatably holding a rectangular substrate by a spin chuck; (h) supplying a solvent for a coating film to a first portion deviated from a rotation center portion of the substrate; (i) supplying a process liquid to a second portion which is at the rotation center of the substrate; and (j) diffusing the process liquid from the second portion to a periphery thereof by rotating the substrate.
In the steps (c), it is preferable that rotation of the substrate is stopped or rotated at low speed, and the process liquid is supplied to the second portion. In this case, the amount of scattered liquid is reduced when supplying the process liquid, and the generation amount of mist is reduced, so that the generation amount of particles is reduced.
Since the solvent is familiar with the process liquid (i.e., the process liquid has a high solubility with respect to the solvent), the solvent does not repel the processing liquid but the process liquid smoothly moves on the substrate when the process liquid supplied onto the substrate is brought into contact with the solvent. The solvent is thinner where the process liquid is a resist solution, for example. Otherwise, the solvent is water where the process liquid is a development liquid, for example.
A coating film forming method comprising the steps of: (g) rotatably holding a rectangular substrate by a spin chuck; (h) supplying a solvent for a coating film to a first portion deviated from a rotation center portion of the substrate; (i) supplying a process liquid to a second portion which is at the rotation center of the substrate; and (d) diffusing the process liquid from the second portion to a periphery thereof by rotating the substrate.
The xe2x80x9cportion (or first portion) deviated from the rotation center of the substratexe2x80x9d indicates a region (or portion) which is deviated from the center point of the substrate when the substrate is rotated by the spin chuck and which is positioned between the center position of the substrate and the peripheral edges. In addition, the xe2x80x9crotation center portion (or second portion) of the substratexe2x80x9d indicates a narrow region (or portion) including the center point of the substrate when the substrate is rotated by the spin chuck and the vicinity of the center point.
The process liquid (or main liquid) supplied from the first nozzle diffuses up to the peripheral edges in the sides of the short edges of a rectangular substrate from the first portion (or the portion at the rotation center portion of the substrate), but is difficult to diffuse (or reach) to the peripheral edges in the sides of the long edges of the rectangular substrate or to the corner portions thereof. In particular, the process liquid (or main liquid) is insufficient at the corner portions of the rectangular substrate. However, the process liquid (or supplementary liquid) supplied from the second nozzle diffuses (or reaches) rapidly and easily to the corner portions. This is because there is only a short distance from the second portion (or the portion deviated from the rotation center portion of the substrate) to the peripheral edges of the rectangular substrate in the long edges of the rectangular substrate or the corner portions thereof.
A coating film forming method comprising the steps of: (k) rotatably holding a substrate by a spin chuck; (l) supplying a solvent for a coating film onto the substrate by a solvent supply nozzle; (m) supplying a process liquid on the substrate by a process liquid supply nozzle; (n) diffusing the process liquid by rotating the substrate; and (p) supplying the solvent to a peripheral portion of the substrate by the solvent supply nozzle.
In so-called pre-wet processing, a solvent is supplied to a substrate prior to resist application processing in order to restrict the consumption of the resist solution. In the present invention, the same nozzle as used in the pre-wet processing is used to remove a film from peripheral edge portions of the substrate. Therefore, the consumption of the resist solution decreases, any specialized equipment is not required additionally to remove a film from the peripheral edge portions of the substrate and position of the nozzle with respect to the substrate can be facilitated.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.